Just after the Nexus 5 announcement, Google also made the system image of Android 4.4 Kitkat available on the Android developers site. Android 4.4 has updated version of Google Play Services and Google Now. The stock Trebuchet launcher is now Google Experience Launcher.
With all the new stuff, Google's Nexus 5 comes with new stock wallpapers. You can download the pack consisting of all 6 wallpapers from below. The resolution of wallpapers is 3966 x 3966 pixels.
Download(6 Wallpapers, 11.3 MB)